The enhancement of recording density of a magnetic disk device has been attained by enhancing the magnetic characteristic of the magnetic head and recording medium, and by shortening the distance from the gap end of magnetic head to the surface of the magnetic layer of the recording medium, i.e., the magnetic spacing.
Currently, the magnetic spacing is about 40 to 50 [nm], depending on the air bearing surface protecting film of a flying head slider that is loaded with a magnetic head and flies on air film, the protecting film or lubricating film on the surface of the medium, and the roughness of the surface of the medium. To realize a recording density of 10 to 20 [Gb] or more per square inches in the future, the magnetic spacing is required to be smaller than 15 [nm].
As one means for such requirement, slide-type magnetic disk devices, which conduct the recording and reproduction while keeping contact-sliding on a recording medium, that can remarkably shorten the distance between a magnetic head and the surface of the magnetic layer of a recording medium have been developed (e.g., H. Hamilton, Journal of Magnetic Society of Japan vol. 15, Supplement No. S2(1991)483, and Japanese patent application No.5-508808).
FIG. 1 is an illustrative front view showing the basic composition of a conventional slide-type magnetic disk device 100. This slide-type magnetic disk device 100 is composed of a slide-type magnetic head 107, a magnetic head slider 101 that is loaded with the slide-type magnetic head 107, and a suspension spring 106 that supports the magnetic head slider 101 and presses it against a magnetic recording medium D.
The suspension spring 106 is connected through a positioning actuator arm 112 with a positioning actuator 102 that moves the slide-type magnetic head 107 on the magnetic recording medium D. The suspension spring 106 is made of a sheet of leaf spring, and presses the magnetic head slider 101 against the magnetic recording medium D, using the bending of the entire leaf spring.
FIGS. 2A and 2B are perspective views showing the details of the magnetic head slider 101 and the suspension spring 106. FIG. 2A shows the suspension spring 106 and the magnetic head slider 101 supported thereby, and FIG. 2B shows the enlarged magnetic head slider 101. FIG. 2C is a partially-broken enlarged perspective view showing a contact pad 108 provided on the lower surface of the magnetic head slider 101. As shown, a yoke 111 is buried in the contact pad 109 formed at the tip of the magnetic head 107, and conducts the contact recording and reproduction, on the suspension spring 106, electric wiring 113 is formed directly.
Although the suspension spring 106 in the above example made is of a sheet of leaf spring, a slide-type magnetic disk device to which a gimbal mechanism is added to improve the follow-up performance to the medium has been also developed. FIG. 3 is an illustrative front view showing the basic composition of such a conventional slide-type magnetic disk device 130. Like parts in FIG. 3 are indicated by like reference numerals as used in FIG. 1, and explanations thereof are omitted herein.
In this conventional example, the magnetic head slider support mechanism is composed of a gimbal 121 to support the magnetic head slider 101, and a beam suspension 106 to support the gimbal 121 and to give a load to the magnetic head 107.
By the way, in conducting the seek or tracking operation on the magnetic recording medium, the suspension composing the slide-type magnetic head support mechanism is required to have high rigidity in the radius and circumference directions of the recording track, and to have sufficient strength to cause a frictional force or viscous fluid force to be generated between the magnetic head slider and the lubricant coated on the surface of the magnetic recording medium.
Also, to allow the magnetic head slider to follow up contacting or having micro clearance with the surface of the magnetic recording medium, the magnetic head slider must also have suitable flexibility as to be able to accept the rolling (i.e., rotation movement around the axial parallel to the running direction of the magnetic recording medium) and pitching (i.e., rotation movement around the axis tangential to the recording track) of the magnetic head slider is simultaneously required.
Furthermore, to obtain the medium follow-up performance, it is important that suitable load is applied to the slide pad on the magnetic head slider. In general, for flying-type sliders, a suspension with one-point pivot is often used.
Since the rigidity of the air film generated at the air bearing surface of the flying slider is very high and a suitable load distribution can be realized by optimizing the shape of the air bearing surface, the suspension is required to receive such application of load as not to prevent the movement characteristic of the slider. For this requirement, the one-point pivot support does not prevent the movement characteristic defined by the air bearing rigidity of the slider since it ideally supports the slider at one point. Therefore, excellent characteristic can be obtained.
However, in the slide-type magnetic head slider, at first, when the pad contacts the magnetic recording medium at one point, it is, at least, required that the slider applies a load to the medium so as to be always kept parallel to the medium. If the pad is even slightly inclined to the medium, part of the magnetic head will jump that much, thereby necessary characteristics of recording and reproduction cannot be obtained.
In applying the one-point pivot load, though the load can be theoretically applied to the pad, it is required that the magnitude and position of the load to be applied are provided at a very high precision. In the gimbal shown in FIG. 3, the contact state of the pivot after assembling is fixed. Therefore, in relation to the assembly tolerance, it is, in substance, very difficult to obtain the uniform contact between the pad and the medium.
On the other hand, in the case of multiple pads (i.e., more than three pads), since the attitude of the slider is determined in a virtual plane of the pad surface, even with the one-pivot load, the jump amount of the pad provided for the magnetic head becomes hard to be affected by the assembly tolerance, compared with the case of one pad.
However, the distribution of surface pressure that the respective pads receive is often dispersed due to the position tolerance of the one-point pivot in the slider. When optimum load distribution is not obtained, the abrasion at part of the pads becomes uneven among the respective pads, thereby incurring biased abrasion.
This biased abrasion is not so serious for the follow-up of track, but, in seeking, the abrasion characteristic becomes uneven between in-seek and out-seek. Therefore, the fine positioning operation cannot be conducted. Also, to attain the ideal one-point pivot support, the rigidity of the suspension has to be considerably increased. Therefore, its weight saving is hard to reduce the weight of the suspension.
Next, surface loading system, instead of the one pivot loading system, is considered. In this system, the entire part of the gimbal spring the supporting the slider applies a load to the slider, and an even load can be theoretically applied to the back surface of the slider. Also, this system is advantageous for weight saving because the load beam and the gimbal can be integrally formed.
However, the surface loading system has a problem that, due to the assembly tolerance, the slider is often subject to some load and moment being continuously applied, therefore increasing the dispersion of load that the respective pads receive.